Whatsapp intregration in my mobile app

I have purchased website and app from codecynon. My app is xamrin platform and my website name is makestube.com. I want to add whatsapp feature in my android application. My website and app specially for video sharing website and I want to store whatsapp number on my content uploader on his profile and when viewers click on his video viewers can see whatsapp icon on video page and when viewers click on whatsapp icon then viewers redirect to whatsapp chat ok. I have whatsapp api also so developer only add this feature in application source code. I have already add whatsapp feature in my website so you can check my website how it works.